websocket_76_erlang.erl

%%--------------------------------------------------------------------
%% @spec build_challenge(Key1::list(),Key2::list(),Key3::binary()) -> binary()
%% @doc Builds the challenge needed by WebSocket Handshake 76 
%% @end 
%%-------------------------------------------------------------------- 

build_challenge(Key1,Key2,Key3)->
  Ikey1 = get_key_number(Key1,[]),
  Ikey2 = get_key_number(Key2,[]),
  
  Blank1 = get_n_blanks(Key1,0),
  Blank2 = get_n_blanks(Key2,0),
  
  Part1 = erlang:list_to_integer(Ikey1) div Blank1,
  Part2 = erlang:list_to_integer(Ikey2) div Blank2,
  
  Ckey = <<Part1:4/big-unsigned-integer-unit:8,Part2:4/big-unsigned-integer-unit:8,Key3/binary>>,
  
  Challenge = erlang:md5(Ckey).


get_n_blanks([],Count)->
  Count;
  
get_n_blanks([S|T],Count) when S == 32->
  get_n_blanks(T,Count+1);

get_n_blanks([_S|T],Count)->
  get_n_blanks(T,Count).

  
get_key_number([],Acc)->
  Acc;

get_key_number([H | T],Acc) when H >= 48 andalso H =< 57->
  get_key_number(T, lists:append(Acc,[H]));
  
get_key_number([_H | T],Acc)->
    get_key_number(T,Acc).